Ducati M900 problem

Hi I am newbie here I don't know where to start, but one thing I know !! is that I need advice with my bike. I got my bike a year ago a 1997 m900, the one problem I have encounter all year is the bike ride lovely, but then all the sudden it dies on me, particularly if I open the throttle.

Sometime it stop even when I am riding slow, I have remove the petrol filter between the tank and the fuel pump, as advice by a mechanic, but it still do it. Sometime it run smoothly, but I don't like riding it as I always return home in the break down truck, lol

Not funny to say the least, I have also replace the petrol vacuum pump with a brand new one, but the problem continues.

I thought of removing the tank and clean it, I have wondered if the is a filter in the tank that cause the trouble. I have also took the bike to the garage but they cant find any fault as it start fine and idle fine too.... ???

Can someone please help, I am desperate for help my Mrs is nagging me, that I have wasted the money.

Your advice will be highly appreciated.

[Albie]

Probably carb Icing Use a premium fuel can help if not a fuel additive. Has yours got the carb heater line and on off tap going to the oil cooler line. That's the one negative of not having fuel injection.

[Flip]

Hmmm fuelling problems can be a pain in the ass to sort unless you have a really good idea of what is causing the issue. This is made a somewhat worse on the early bikes with a rather basic vacuum controlled fuel tap and a vacuum fuel pump of which only the pump is re-buildable).

So, firstly is it actually the pump you have replaced or the tap?

Secondly, are you saying you are running it without a fuel filter at all?

The filter really wants to be there as there isn't one in the tank (like the later bikes) and so any bit of grit getting into the diaphragms of the pumps will likely cause havoc and give further problems.

Personally I would be checking the easy things first such as the fuel tank breather pipe as it can clog at the tank end or at the 'exposed in the road crap' quite easily and this usually shows itself as a hissing sound when you open the fuel cap.

Next, make sure all the fuel and vacuum pipes are in good condition with no splits and not getting kinked under the tank.

But with the bike getting on for twenty years old (like mine) ideally I would be going through the whole lot and replacing everything along with giving the tank a good flush out.

Last year, I did just that and went through the entire fuel system of my 1997 90 replacing almost everything after experiencing what I believe was vapour lock (only ever showed up on hot days when in heavy traffic and at filtering speeds). I have never had carb icing cause any more problem than it running a bit rough and farting around and it only shows up once the motor is warmed up a bit say around five miles into a ride.

Some of the refresh I did can be found here:
http://www.ukmonster.co.uk/monster/s...hlight=refresh

[Darren69]

Vacuum lock maybe? Check tank breathers are clear as previously stated.

[Dirty]

First thing I'd replace is the mechanic that told you to 'fix' the problem by running it without a fuel filter

[slob]

Originally Posted by Dirty

First thing I'd replace is the mechanic that told you to 'fix' the problem by running it without a fuel filter

Damn right, good way to prove it's not a blocked fuel filter, lousy long term solution.

Hi thanks for quick reply, sorry for ignorance, but I don't know what carb heater line is, maybe I don't deserve a bike, by the way my bike doesn't have a on and off tap ....thanks, I don't put new value needle in the carbs.... thanks

Hi thanks for that useful advice I will try that, flushing the tank and replacing the pipes, the pipe under the tank is not kinked.... or trapped, the mechanic did block the two pipes out of the tank because it was licking with fuel before I replace the vacuum tap, my bike doesn't have that tap you are talking about �� Or maybe I don't know what you talking about lol ..... anyway as to the filter the machenic has removed it as he said, when the bike get hot and the filter is near the engine, the heat trap the fuel, the bike behaves like it has run out fuel or fuel starvation. Thanks for the advice I will put the filter back in.

Hi me again, sorry for my ignorance, now I have seen your picture of your project, I do have a vacuum tap that's the one I have replaced and not the main fuel pump at the front end lol

���� hi you hit nail on its head lol

[Dirty]

Put a new filter in, they are cheap as chips.

Of course you deserve the bike. This is all just a useful learning curve

[Darren69]

Isn't there a low pressure fuel pump and filter in the tank on these?

[Dennis menace]

If it is a '97 then Stein Dinse shows an in line filter, rubber mounted on the frame to a vacuum type pump. I had a similar arrangement on my M600. The 'vacuum' is provided by a take off from the air intake so that connection has to be good. Also, it is easy to get the pipe connections the wrong way round on the pump if the pump has been messed with. Definitely worth making sure the tank air vent is clear by blowing it through from the fuel cap opening with an air line and making sure the flap valve in the petrol cap is not blocked or stuck shut. Both will cause fuel starvation eventually.

[Nasher]

Another possibility.

Has the bike had the little plastic carb breather containers removed?
Or the carb breather tubes mucked about with at all.

I had a similar issue as you describe on my M900 that had been modified by several different owners before it came into my hands.

I was tidying up some of the old mods to bring them up to my standard.
One of these was the carb breather tubes had been chopped off a few inches below the carbs as the breather boxes attached to the frame had been removed.
The Vacuum fuel tap had also been removed and replaced with a simple on-off version.

If I parked the bike up and forgot to turn the fuel tap off, fuel dripped out of the breathers down onto the top of the Horizontal cylinder. Luckily it took a while for the fuel to drip, long enough for the engine to have cooled down.

I found some of the correct size tube to replace the carb breathers and routed them down the frame to below the engine.
The bike ran OK at slow speeds, but once at a decent speed for more than a few seconds it ran out of fuel. I had to pull over and let the float bowls refill before it would restart.

I blamed a High/Low pressure area under the engine for affecting the float height.
I tried the longer hoses in three different positions on the bike, but it kept doing the same thing.
Eventually at the side of the road I cut the new pipes off in the same position as the previously ‘modified’ ones and it’s run fine ever since.

I plan to fit a vacuum tap, but for the last year or so have just remembered to turn the fuel tap off.

I’d also take a good look at all the vacuum hose to the fuel tap.

Nasher.

[Flip]

Here is a schematic of the fuel system which might help you- listed as a 750 but identical to a 900:

Originally Posted by Darren69

Isn't there a low pressure fuel pump and filter in the tank on these?

No Darren, on the carb'd bikes the fuel filter is external and the pump is mounted to the frame, it's a Mikuni item often seen on snow mobiles apparently:



The three takes offs are: Fuel in, fuel out and vacuum to the vertical cylinder intake to work the diaphragm.

Originally Posted by Dennis menace

If it is a '97 then Stein Dinse shows an in line filter, rubber mounted on the frame to a vacuum type pump. I had a similar arrangement on my M600. The 'vacuum' is provided by a take off from the air intake so that connection has to be good. Also, it is easy to get the pipe connections the wrong way round on the pump if the pump has been messed with. Definitely worth making sure the tank air vent is clear by blowing it through from the fuel cap opening with an air line and making sure the flap valve in the petrol cap is not blocked or stuck shut. Both will cause fuel starvation eventually.

The very early 900's had their fuel filters mounted as you describe but I'm not sure if SD have got their photos quite right. All the '97ish 900's I have seen are mounted like this which they list as being for a 600/750 (although it is quite likely if ordered you would receive the correct part of course):